The present invention relates to the use of tertiary amino alkyl amides as catalysts for producing polyurethane foams.
The present invention relates to tertiary amino alkyl amide catalysts for producing polyurethane foams. Polyurethane foams are widely known and used in automotive, housing and other industries. Such foams are produced by reaction of a polyisocyanate with a polyol in the presence of various additives. One such additive is a chlorofluorocarbon (CFC) blowing agent that vaporizes as a result of the reaction exotherm causing the polymerizing mass to form a foam. The discovery that CFCs deplete ozone in the stratosphere has resulted in mandates diminishing CFC use. Production of water blown foams, in which blowing is performed with carbon dioxide (CO2) generated by the reaction of water with the polyisocyanate, has therefore become increasingly important. Tertiary amine catalysts are typically used to accelerate blowing (reaction of water with polyisocyanate to generate CO2) and gelling (reaction of polyol with isocyanate).
The ability of the tertiary amine catalyst to selectively promote either blowing or gelling is an important consideration in selecting a catalyst for the production of a particular polyurethane foam. If a catalyst promotes the blowing reaction to a too high degree, much of the CO2 will be evolved before sufficient reaction of isocyanate with polyol has occurred, and the CO2 will bubble out of the formulation, resulting in collapse of the foam. A foam of poor quality will be produced. In contrast, if a catalyst too strongly promotes the gelling reaction, a substantial portion of the CO2 will be evolved after a significant degree of polymerization has occurred. Again, a poor quality foam will be produced, this time characterized by high density, broken or poorly defined cells, and other undesirable features.
Tertiary amine catalysts generally are malodorous and offensive and many have high volatility due to their low molecular weight Release of the tertiary amine during the foam processing may present significant safety and toxicity problems, and release of residual amine from customer products is generally undesirable.
Amine catalysts which contain amide functionality derived from carboxylic acids with long chain alkyl groups (C6 or higher) and fatty acids have an increased molecular weight and hydrogen bonding ability and reduced volatility and odor when compared with related structures which lack this functionality. Furthermore, catalysts which contain amide functionality chemically bond into the polyurethane polymer during the reaction and are not released from the finished product. Catalyst structures that embody this concept are typically of low to moderate activity and promote both the blowing (water-isocyanate) and the gelling (polyol-isocyanate) reactions to varying extents.
U.S. Pat. No. 4,242,467 discloses the use of morpholino and piperazino substituted ureas as catalysts for producing polyurethane foams.
U.S. Pat. No. 4,644,017 discloses the use of certain diffusion stable amino alkyl ureas having tertiary amino groups in the production of a polyisocyanate addition product that does not discolor or change the constitution of surrounding materials. Specifically taught are Catalyst A and Catalyst D which are reaction products of dimethylamino-propylamine and urea.
U.S. Pat. No. 4,007,140 discloses the use of N,Nxe2x80x2-bis(3-dimethylaminopropyl)urea as a low odor catalyst for the production of polyurethanes. The use of N-(3-dimethylaminopropyl)-formamide is also described as a catalyst to make polyurethane foams.
U.S. Pat. No. 4,012,445 discloses the use of beta-amino carbonyl compounds as catalysts for the production of polyurethane foams. In these catalysts, the beta-amino part is present as a dialkylamino or a N-morpholino or a N,Nxe2x80x2-piperazino heterocyclic nucleus and the carbonyl part is present as an amido or ester group.
U.S. Pat. No. 4,735,970 discloses a process for the production of cellular polyurethanes using special amine-CO2 adducts and homogeneous mixtures of these adducts. The use of N-(3dimethylaminopropyl)-formamide is also described as a catalyst to make polyurethane foams.
U.S. Pat. No. 5,200,434 discloses the use of amide derivatives of alkylene oxide polyethers and their uses in polyurethane foam formulation.
U.S. Pat. Nos. 5,302,303, 5,374,486, and 5,124,367 disclose the use of fatty amido amines as a component necessary for the stabilization of isocyanate compositions containing flame-retardants. The shelf-life stability of isocyanate-reactive compositions is often adversely affected by the addition of flame-retardants, especially those based on phosphorous, zinc, antimony, and aluminum. The use of fatty amino amides improves the storage stability of these isocyanate mixtures.
The present invention relates to a method for preparing a polyurethane foam which comprises reacting an organic polyisocyanate and a polyol in the presence of water as a blowing agent, a cell stabilizer, a gelling catalyst, a blowing catalyst, and a tertiary amine amide catalyst composition. The catalyst composition is represented by the formula I: 
wherein A represents CH or N;
R1 represents hydrogen or 
n is an integer from 1 to 3;
R2 and R3 each represent hydrogen or a C1-C6 linear or branched alkyl group;
R4 and R5 each represent a C1-C6 linear or branched alkyl group when A represents N, or together R4 and R5 represent a C2-C5 alkylene group when A represents N; or together
R4 and R5 may be a C2-C5 alkylene group containing NR7 when A represents CH or N,
where R7 is selected from the group consisting of hydrogen, a C1-C4 linear or branched alkyl group, and 
and; R6 represents a C5-C35 linear or branched alkyl, alkenyl, or aryl group.
The present invention provides a reactive catalyst composition for making a water-blown flexible polyurethane foam. The catalyst composition may contain reactive Nxe2x80x94H groups from an amide functionality that can react with isocyanates causing the immobilization of the catalyst into the polyurethane polymer yielding polyurethane foams that have no amine emissions.
The use of these catalysts in conjunction with gelling or blowing co-catalysts improves physical properties and enhances processibility of the foam. As gelling catalysts, these amide catalysts in conjunction with blowing co-catalysts improve the airflow of the foam. Improved airflow means improved porosity and openness of the foam which is an indication of improved dimensional stability of the foam. As gelling catalysts, these amide catalysts in conjunction with blowing co-catalysts also improve, i.e., reduce, the force-to-crush of the foam. Reduced force-to-crush means the foam is more easily compressed which Is an important advantage for minimizing foam shrinkage during processing. As blowing catalysts, these amide catalysts in conjunction with gelling co-catalysts improve the load bearing properties of the foam. That such high molecular weight compounds have good catalytic activity in the production of a polyurethane is surprising, since the prior art suggests that they will react at the time of mixing and be incorporated into the polymer matrix early in the polyurethane process thus limiting their mobility.
The present invention provides a method for making polyurethane foams using a reactive catalyst composition that comprises a tertiary amino alkyl amide. The amide is derived from a carboxylic acid of the type R6xe2x80x94CO2H, where R6 is a C5-C35 linear or branched alkyl, alkenyl, or aryl group. The reactive catalyst compositions are typically used in the presence of a mono- and/or bis-(tertiary amino alkyl) urea gelling catalyst and a blowing catalyst. The catalysts may contain reactive Nxe2x80x94H groups from an amide functionality which enables the catalyst to react with, and be immobilized into, the polyurethane matrix producing polyurethane foams which have no amine odor or emissions.
The method of the present invention is more fully described in copending patent applications entitled xe2x80x9cTertiary Amino Alkyl Amide Polyurethane Catalysts Derived from Long Chain Alkyl And Fatty Carboxylic Acidsxe2x80x9d and xe2x80x9cImproving The Physical Properties Of Polyurethane Foams Using Tertiary Amino Alkyl Amide Catalystsxe2x80x9d, filed by applicant concurrently with the present patent application and assigned to the assignee of this application, which applications are hereby incorporated by reference.
The reactive catalyst composition of the present invention may be represented by three parts: the tertiary amine portion, the amide portion, and the long chain alkyl portion (R6). The tertiary amine portion provides catalysis for producing polyurethane foams. The amide portion provides functionality which enables the catalyst to react into the polyurethane matrix such that the resulting polyurethane foams have no amine odor or emissions. The long chain alkyl portion enables the catalysts to improve its performance by improving the physical properties such as tear and tensile strength, % break elongation and compression sets.
Example 7 shows that conventional dialkyl amino amides, where the amide portion is derived from a simple carboxylic acid, such as formic acid or acetic acid, do not perform as well as their long chain alkyl chain or fatty acid counterparts. Amino amide catalysts, such as N-(3-dimethylaminopropyl)-formamide or N-(3-dimethylaminopropyl)acetamide, do not perform by themselves according to the current industry standards (DABCO(copyright) BLV catalyst). The performance limitations of these compounds are very well recognized in the art and similar limitations are expected for related structures. Compounds such as N-(3dimethylaminopropyl)-2-ethylhexamide or N-(3-dimethylaminopropyl)-lauramide would be expected to perform like N-(3-dimethylaminopropyl)-formamide and N-(3-dimethylaminopropyl)-acetamide with the additional limitation of having higher molecular weights that typically results in high usage levels.
In Example 10, combinations of N-(3dimethylaminopropyl)-cocoamide (DMAPA-cocoamide) and a gelling catalyst (DABCO(copyright) NE1060 catalyst) were used together with a blowing catalyst (TEXACAT(copyright) ZF-10 catalyst). The physical properties of the resulting foams were measured and compared with the current industry standards (DABCO(copyright) NE1060 catalyst). The results show that when the DABCO(copyright) NE1060 catalyst was progressively and partially replaced by DMAPA-cocoamide, the physical properties of the resulting foams consistently approached the industry standard. These results demonstrate that the physical properties of foams can be improved and systematically changed to resemble foams made with fugitive catalysts that are today""s industry standards.
Surprisingly, the examples presented in this disclosure clearly show that higher alkyl chain and fatty acid derivatives perform better than their lower molecular weight counterparts because the rate of rise profiles can, in most cases, be superimposed to current fugitive industry standards. The Me2N-moieties in N-(3-dimethylaminopropyl)-formamide and in N-(3dimethylaminopropyl)-acetamide are catalytically less active than the Me2N-moiety in, for example, N-(3dimethylaminopropyl)-lauramide. Moreover, catalyst usage remained modest even though the molecular weights of the fatty amides are much larger than those of the standards. Although the higher activity of the present catalyst compositions can explain their modest usage level, the reason for this enhanced activity is not obvious and not clearly understood. In addition, the benefit is not limited to a kinetic rate matching but also to a systematic improvement of foam physical properties when a conventional non-fugitive gelling catalyst is systematically replaced by the new catalyst composition.
The catalyst compositions according to the present invention catalyze the reaction between an isocyanate functionality and an active hydrogen-containing compound, i.e., an alcohol, a polyol, an amine, or water. The catalyst compositions also catalyze the urethane (gelling) reaction of polyol hydroxyl groups with isocyanate to make polyurethanes and the blowing reaction of water with isocyanate to release carbon dioxide for making foamed polyurethanes.
The flexible polyurethane foam products are prepared using any suitable organic polyisocyanates known in the art including, for example, hexamethylene discarnate, phenylene discarnate, toluene discarnate (TDI) and 4,4xe2x80x2-diphenylmethane discarnate (MDI). Especially suitable are the 2,4- and 2,6-TDI""s individually or together as their commercially available mixtures. Other suitable isocyanates are mixtures of diisocyanates known commercially as xe2x80x9ccrude MDIxe2x80x9d, marketed as PAPI by Dow Chemicals, which contains about 60% of 4,4xe2x80x2-diphenylmethane discarnate along with other isomeric and analogous higher polyisocyanates. Also suitable are xe2x80x9cprepolymersxe2x80x9d of these polyisocyanates comprising a partially prereacted mixture of a polyisocyanate and a polyether or polyester polyol.
Illustrative examples of suitable polyols as a component of the polyurethane composition are the polyalkylene ether and polyester polyols. The polyalkylene ether polyols include the poly(alkylene oxide) polymers such as poly(ethylene oxide) and poly(propylene oxide) polymers and copolymers with terminal hydroxyl groups derived from polyhydric compounds, including diols and triols; for example, ethylene glycol, propylene glycol, 1,3-butane diol, 1,4-butane diol, 1,6-hexane diol, neopentyl glycol, diethylene glycol, dipropylene glycol, pentaerythritol, glycerol, diglycerol, trimethylol propane and similar low molecular weight polyols.
In the practice of this invention, a single high molecular weight polyether polyol may be used. Also, a mixture of high molecular weight polyether polyols such as mixtures of di- and tri-functional materials and/or different molecular weight or different chemical composition materials may be used.
Useful polyester polyols include those produced by reacting a dicarboxylic acid with an excess of a diol, for example, adipic acid with ethylene glycol or butanediol, or reaction of a lactone with an excess of a diol such as caprolactone with propylene glycol.
In addition to the polyester and polyethers polyols, the master batches, or premix compositions, frequently contain a polymer polyol. Polymer polyols are used in polyurethane foams to increase the foam""s resistance to deformation, i.e., to increase the load-bearing properties of the foam. Currently, two different types of polymer polyols are used to achieve load-bearing improvement. The first type, described as a graft polyol, consists of a triol in which vinyl monomers are graft copolymerized. Styrene and acrylonitrile are the usual monomers of choice. The second type, a polyurea modified polyol, is a polyol containing a polyurea dispersion formed by the reaction of a diamine and TDI. Since TDI is used In excess, some of the TDI may react with both the polyol and polyurea. This second type of polymer polyol has a variant called PIPA polyol, which is formed by the insitu polymerization of TDI and alkanolamine in the polyol. Depending upon the load-bearing requirements, polymer polyols may comprise 20-80% of the polyol portion of the master batch.
Other typical agents found in the polyurethane foam formulations include chain extenders such as ethylene glycol and butane diol; cross-linkers such as diethanolamine, diisopropanolamine triethanolamine and tripropanolamine; blowing agents such as water, CFCs, HCFCs, HFCs, pentane, and the like; and cell stabilizers such as silicone surfactants.
A general polyurethane flexible foam formulation containing a gelling and a blowing catalyst according to the invention would comprise the following components in parts by weight (pbw):
The catalyst composition comprises a tertiary amino alkyl amide composition represented by the formula I: 
wherein A represents CH or N;
R1 represents hydrogen or 
n is an integer from 1 to 3;
R2 and R3 each represent hydrogen or a C1-C6 linear or branched alkyl group;
R4 and R5 each represent a C1-C6 linear or branched alkyl group when A represents N, or together R4 and R5 represent a C2-C5 alkylene group when A represents N; or together R4 and R5 may be a C2-C5 alkylene group containing NR7 when A represents CH or N, where R7 is selected from the group consisting of hydrogen, a C1-C4 linear or branched alkyl group, and 
and; R6 represents a C5-C35 linear or branched alkyl, alkenyl, or aryl group.
Preferably, R1, R2, and R3 each represent hydrogen and R4 and R5 each represent a methyl group when A represents N. R4 and R5 together may represent xe2x80x94CH2CH2N(CH3)CH2xe2x80x94 when A represents CH. Preferably, n represents 2 or 3.
Illustrative examples of dialkylamino amides derived from higher alkyl and fatty acids are: the N-(3-dimethylaminopropyl)-amides, the N-(2-dimethylaminoethyl)-amides, the N-methyl-3-aminoethyl pyrrolidine amides, the 4,10-diaza-4,10,10-trimethyl-7-oxa-undecaamine amides, and any dimethylamino- or dialkylamino-alkyl, or alkyl substituted amides derived from 2-ethylhexanoic, coconut oil fatty, tall oil fatty, caproic, heptylic, caprylic, pelargonic, capric, hendecanoic, lauric, tridecanoic, myristic, pentadecanoic, palmitic, margaric, stearic, oleic, linoleic, linolenic, ricinoleic, nonadecanoic, arachidic, heneicosanoic, behenic, tricosanoic, lignoceric, pentacosanoic, cerotic, heptacosanoic, montanic, nonacosanoic, melissic, hentriacontanoic, dotriacontanoic, tritriacontanoic, tetracontanoic, hexatriacontanoic or their aliphatic or aromatic substituted derivatives such as 9- and 10-phenylstearic and related structures.
The preferred amides are N-(3-dimethylaminopropyl)-amides. The preferred acids are selected from the group consisting of 2-ethylhexanoic, coconut oil fatty, and tall oil fatty acids.
The amides are prepared by reacting a carboxylic acid and the corresponding tertiary alkyl amine in the appropriate molar ratios at elevated temperatures of from 80xc2x0 C. to 300xc2x0 C., preferably 100xc2x0 C. to 200xc2x0 C., with water being driven off. The amides can be further purified by distillation or chromatography as known in the art.
The amides can be used in conjunction with a gelling catalyst, such as a tertiary amine or a suitable transition metal catalyst, and/or a blowing catalyst depending upon the processing advantages desired.
Examples of suitable tertiary amine gelling catalysts include, but are not restricted to, diazabicyclooctane (triethylenediamine), supplied commercially as DABCO(copyright) 33LV catalyst by Air Products and Chemicals Inc., quinuclidine and substituted quinuclidines, substituted pyrrolidines and pyrrolizidines. Examples of suitable tertiary amine blowing catalysts include, but are not restricted to, bis-dimethylaminoethyl ether, commercially supplied as DABCO(copyright) BL11 catalyst by Air Products and Chemicals, Inc., pentamethyl-diethylenetriamine and related compositions, higher permethylated polyamines, 2-[N-(dimethylaminoethoxyethyl)-N-methylamino]ethanol and related structures, alkoxylated polyamines, imidazole-boron compositions and amino propyl-bis(aminoethyl)ether compositions.
A catalytically effective amount of the catalyst composition comprising the amide and a tertiary amine gelling or blowing catalyst may be used in the polyurethane formulation. More specifically suitable amounts of the catalyst composition may range from about 0.01 to 10 parts by wt per 100 parts polyol (pphp) in the polyurethane formulation, preferably 0.05 to 2 pphp.
The catalyst composition may be used in combination with, or also comprise, other tertiary amines, organotin or carboxylate urethane catalysts well known in the urethane art.
Although the present invention has been described as useful for preparing flexible polyurethane foams, the invention may also be employed to prepare semi-flexible and rigid polyurethane foams. Rigid polyurethane foams can be distinguished from flexible polyurethane foams by the presence of higher isocyanurate levels in the rigid foam. Flexible foams typically use polymer polyol as part of the overall polyol content in the foam composition, along with conventional triols of 4000-5000 weight average molecular weight (Mw) and hydroxyl number (OH#) of 28-35. In contrast, rigid polyurethane foam compositions use 500-1000 Mw polyol with 3-8 hydroxyl functionalities and OH# of 160-700. Rigid foams can also be distinguished from the flexible foams by the isocyanate (NCO) index of the foam composition. Rigid foam compositions typically use a 100-300 NCO index whereas flexible foam compositions typically require a 70-115 NCO index.
A general polyurethane rigid insulating foam formulation containing the catalyst composition according to the invention would comprise the following components in parts by weight (pbw):
For making lamination (insulation board) and appliance foams the NCO index is typically 100-300; for making open cell foam the NCO index is typically 100-120 and the foam is usually all water blown.
Semiflexible molded foams have been utilized for many applications in the automotive area. The major applications are instrument panels and interior trims. A typical semiflexible foam formulation containing the catalyst composition according to the invention comprise the following components in parts by weight (pbw):
The two main components are the base polyol and copolymer polyol (CPP). The base polyol is utilized at levels between 70-100%. The molecular weight of base polyols range from 4500 to 6000 for triols and 2000 to 4000 for diols. Ethylene-oxide-capped, polyether polyols have replaced most polyester polyols as the base polyol. The primary hydroxyl content is usually grater than 75% and the capping range is typically 10-20%. The other major component is CPP, which are used at levels of 0 to 20%. The base polyol and CPP are blended with low molecular weight cross linkers to build hardness and promote faster demolding. The level of cross linker varies depending on the hardness requirement of the finished part. Water levels are chosen to give free rise densities from 3 to 6 pounds. Cell openers are also utilized in semiflexible foams to reduce the internal foam pressure during the cure cycle and thus reduce pressure-relief voids and xe2x80x9cparting linesxe2x80x9d. Adhesion promoters can be added, depending upon the quality of the vinyl skin, to improve the adhesion between the polyurethane foam and the vinyl skin. The use of the catalyst composition of the present invention can reduce the discoloration of the vinyl skin typically observed with conventional amine catalysts because the Nxe2x80x94H group of the amide functionality can react with the isocyanate to form a covalent bond with the polyurethane polymer.